The present invention is directed generally to brewing apparatus for heated beverages, such as coffee and tea, and more particularly to brewing apparatus having a hot water reservoir and a temperature interlock circuit which prevents dispensing hot water from the reservoir when the temperature of the hot water falls below a predetermined minimum temperature level.
One known type of brewing apparatus for making heated beverages includes a reservoir within which a volume of water to be displaced is heated by a resistance heating element to a predetermined brewing temperature. In a preferred form of such brewing apparatus, such as the coffee maker described in U.S. Pat. No. 4,413,552, heated water is displaced from the top portion, or outlet zone, of the reservoir by cool or cold water entering the bottom portion, or inlet zone, and discharged onto ground coffee or tea held in a brewer funnel lined with a disposable filter. Freshly brewed coffee or tea discharging from the brewer funnel is collected in a serving beaker.
Cold water is admitted in batches of predetermined volume to the reservoir of such brewing apparatus to displace the heated water delivered to the brewing funnel. In pour-in type beverage brewers, such as described in the aforementioned U.S. Pat. No. 4,413,552, a volume of cold water sufficient to produce the desired volume of beverage to be brewed is poured into a cold water basin from which it flows by gravity into the reservoir to displace an equal volume of hot water to the brewing funnel. In automatic type beverage brewers, such as described in U.S. Pat. Nos. 3,793,934 and 4,478,139, a valve is opened by electrical or manual means for a predetermined period of time to periodically deliver the desired volume of cold water to the reservoir.
One problem with such displacement brewers has been the possibility that, with repeated uses over a short time interval, the water displaced from the reservoir for brewing may not be of sufficiently high temperature for brewing purposes, resulting in an inferior beverage. The present invention avoids this possibility by providing an interlock which prevents the displacement of water from the reservoir when the temperature of the water in the reservoir falls below a predetermined minimum level. In a particularly advantageous implementation of the invention, a single temperature sensing element in the reservoir provides both the interlock function and regulation of temperature in the reservoir.